1. Field of the Invention
The invention relates generally to magnet assemblies and in particular to a method for constructing a permanent magnet assembly by using a frame to restrain the movement of magnets.
2. Description of the Related Art
Numerous methods exist for construction of magnetic assemblies. The desired configuration and size of the magnetic assembly often dictates the method required for construction of the assembly, due, at least in part, to the large forces inherent in magnetic materials.
Permanent magnet materials function like any other material until magnetized by an external source. Manufacturing operations on permanent magnet materials such as grinding, slicing, etc. are well established, and pose no significant challenges to those equipped with the proper tools. Although charged magnetic materials can be machined, unmagnetized stock is preferred.
Magnetic materials are frequently altered by machining operations to shape the materials and to adjust the magnetic field characteristics of the materials. The altered, unmagnetized, magnetic materials may be assembled and then magnetized to full saturation, to minimize the exposure of assembly personnel to potentially dangerous forces that would otherwise exist if assembling magnetized materials. Although it is preferred that all magnets be charged after assembly, the sheer size and, more importantly, orientation of magnetic materials in some assemblies require personnel to work with fully magnetized materials. The associated dangers are significant and compounded as the size of the magnetized materials increases.
Magnetic assemblies may involve permanent magnets positioned in a manner that counters the natural alignment tendencies of the magnets, creating very large torques and forces that may lead to self-destruction if not properly restrained, during the assembly process.
Adhesives are currently the main fastening mechanism in the majority of magnetic assemblies. During the assembly process, external restraints are placed on the magnet being loaded into the assembly. These restraints are typically 3-axis ball screw driven linear slides. Adhesive is placed on the contact surfaces of the target magnet, which is then placed into its location in the assembly and held there until the adhesive has set.
Magnets being installed in magnet assemblies often experience three orthogonal forces. These forces generally differ in magnitude making it difficult to maintain the magnet's physical orientation as it is being assembled. Increased magnet sizes or certain assemblies can create forces that can approach hundreds or thousands of pounds and make hand assembly difficult, dangerous, or even impossible. As stated above a mechanical means of assembling such structures is required. Such means can become prohibitively large and costly. Furthermore, once the adhesive is set and the mechanical restraints removed, the loads imparted on the target magnet are fully absorbed by the adhesive. Although this has proven to be an acceptable method of assembly, broken or faulty bond lines may exist causing magnets to come loose.
Once a magnet assembly is completed, an exoskeleton of metal is often placed around the unit to act as the last line of defense against any failed bond line.
Nonetheless, at times during the assembly process the adhesive is the only fastening mechanism used to constrain the vast amounts of energy stored in the unit.
Magnets may be improperly oriented or defectively attached during construction of the assembly. Repair of magnets assembled in incorrect orientations can be difficult as well as dangerous. Attempting to separate faulty magnets may also sacrifice the integrity of any other bond lines or damage any other magnets in the system.